as a beginner you 1st have to get your rhythm. the best way to do this is with a jump rope. once you get your rhythm you can start developing your footwork with the jump rope, as you see many boxers do for a large part of their training. you're falling off balance cos your timing is not on, when your throwing a punch your whole body needs to be coordinated. when you get your rhythm and footwork with the junp rope move on to shadow boxing in front of a mirror and you will see what you're not doing right, this way you can correct it. hope this helps.